Neoadjuvant chemotherapy may optimize the extent of resection of World Health Organization grade II gliomas: a case series of 17 patients

The involvement of eloquent brain areas may preclude the total/subtotal surgical resection of diffuse low-grade gliomas (DLGGs). The feasibility and functional tolerance of neoadjuvant chemotherapy have been demonstrated in such cases. The present study assesses the clinical and radiological impact of neoadjuvant chemotherapy on the natural course of DLGG. Seventeen patients without feasible surgical resection (infiltration of functional areas and/or large contralateral extension) were retrospectively selected. Temozolomide based neoadjuvant chemotherapy was initiated, inducing a tumor volume decrease and allowing a functional based maximal surgical resection. The median follow-up since initial radiological diagnosis was 5.9 years (range, 1.4-11). The median time to malignant transformation was 5.9 years. Six patients (35 %) had 1p19q codeletion, 12 patients (70 %) with IDH mutation and MGMT promoter methylation, and eight patients (47 %) had p53 overexpression. Chemotherapy reduced tumor volume (median -35.6 %, range -61.6 to -5.1 %) in contralateral hemisphere through the corpus callosum in seven cases (41 %) and in ipsi-lesional functional areas in ten cases (59 %). Chemotherapy significantly decreased the imaging tumor growth (measured by the velocity of diametric expansion VDE) with a median of -3.2 mm/year (range, -29.8 to -0.9 mm/year) (p < 0.001). A tumor volume decrease of more than 20 % was correlated with a lower postoperative residual tumor (median 2 cc, p = 0.04), a greater extent of resection (93.1 vs. 89.5 %), a higher probability of total/subtotal removal. Neoadjuvant chemotherapy with Temozolomide could optimize the surgical resection of DLGGs and could impact their natural history. Further large prospective studies with long-term follow-up are needed.